Machine-switching telephone system



L. POLINKOWSKYJ MACHINE SWITCIHNG TELEPHONE SYSTEM APPLICATION FILED .Aus.21. 191s.

138L431. PatentedJune 14,1921.

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MACHINE SWITCHING TELEPHONE SYSTEM.

APPLICATION FTLED Aue.2. .191s.

L. POLINKQWSKY.

MACH INE SWITCHING TELEPHONE SYSTEM. APPLICATION FILED AuG 27. 1918.

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MACHINE SWITCHING TELEPHONE SYSTEM.

APPLICATION FILED Aue.27,1e1e.

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MACHINE SWITCHING TELEPHONE SYSTEM.

APPLICATION FILED AUG-27. 1918.

1,381,431 Patented June 14, 1921.

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L. PO LINKOWSKY.

MACHINE SWITCHING TELEPHONE SYSTEM.

APPLICATION FILED AUG.27| I918.

Patented June 14, 1921.

- 6 SHEETSSHEET 6 5 6,

UNITED STATES PATENT OFFICE.

LIPA. POLINKOWSKY, 0F HYDE PARK, LONDON, ENGLAND, ASSIGNOR TO WESTERN ELECTRIC COMPANY, INCORTORATED, OF NEW YORK N. Y., A CORPORATION OF NEW YORK.

MACHINE-SWITCHING TELEPHONE SYSTEM.

Specification of Letters Patent. Patented June 14, 1921,

Application filed August 27, 1918. Serial No. 251,603.

To all whom. it may concern Be it known that I, LIPA POLINKOWSKY, a citizen of Russia, residing at 70 VVestbourne Terrace, Hyde Park, London, England, have invented certain new and useful Improvements in Machine-Switching Telephone Systems, of which the following is a full, clear, concise, and exact description.

This invention relates to machine switching telephone systems and moreparticularly to systems wherein, in addition to the usual or ordinary service provided for the interconnection of the subscribers stations of an exchange network, a special service is provided such, for example, as the service in which the subscribers stations of such network are interconnected with stations of some other network reached over toll or junction lines extending between the respective networks.

A particular feature of the invention involves a novel arrangement of circuits and apparatus by means of which the extension of an incoming call over a toll operators position is produced to the desired line in an expeditious and simple manner. More specifically this feature involves such an arrangement of the apparatus that the control of the extension of the call is divided between the manual toll operator and the semi-automatic switching operator, the division of duties being such that the manual toll operator is able to handle a callprecisely as though it were call to a manual switchboard, the semi-automatic switching operator exerising the necessary controlto ex tend the call over the machine switching apparatus, which operation she is in the best position to perform with etliciency and despatch. To this end the semi-automatic switching operator receives an order with regard to an incoming call from the manual toll operator over an order wire in the usual manner, and, informing the manual toll op erator of the trunk assigned to the call, depresses the corresponding assignment key to initiate the activity of the machine switching apparatus to extend the call, subseouentlv controlling the extension of the call to the desired line by the usual number key apparatus and determining whether when the line has been found, if such line is busy, the existing connection therewith is to be broken down. The circuits and apparatus provided for the purposes mentioned involve also novel dispositions and use of visual and other signals which will be more specifically referred to hereinafter.

Still another feature of the invention involves that the breaking down of an established connection to the line with which the special service call is to be extended is caused by a temporary condition placed upon a terminal individual to such desired line, such breaking down condition being removed after the duration of a brief interval suflicient to insure the restoration of the apparatus involved in such previous connection.

Another feature related to the feature just mentioned provides that, after the establishment and removal of the breaking down condition on the terminal of the desired line already engaged with the previous connection, a busy tone is placed upon the same terminal, which tone will be received by subsequent special service calls attempting extension to the same desired line, that is, the circuits and apparatus are so arranged that in the extension of a special service call to a desired line already engaged with a call over which such special service call takes precedonce, there is first applied a breaking-down condition to the test terminal of the desired line and which condition is then removed, there being applied thereafter to such test terminal a distinctive busy tone indicating that such desired line is in use in connection with a special service call.

Still another feature of the invention provides that in systems of the character referred to, that is, wherein a special service call first passes over a toll operators manual position, then over a switching operators semi-automatic controlling position and tinally over a series of automatic switches terminating in a final selector switch, means provided at the first group selector switch placed upon the completion of the selectoperations first under the control of the operator then under the control of final selector switch and the apparatus associated therewith, such means serving,

unless operated in the required manner from the toll operators position and then from the final selector switch, to prevent the through connection from such switching opcrators position to the desired line. In the particular form of the invention herein disclosed, such means takes the form of a sequence switch which is first retained in a given position until the extension of the special service call from the toll operators position to the assigned trunk has been completed and subsequently is retained in a particular position thereof responsive to the finding busy of the desired line at the final selector,being moved from such position if the desired line is idle, but remaining in such position and causing the flashing of a busy lamp if such desired line is found busy.

A related feature of the invention provides that a special service call having been extended over a manual toll operators position to a semiautomatic controlling switching operators position and such switching operator having established a controlhng condition to produce the extension of such special service call to the terminals of the desired line, the extension of the telephonic circuit of such desired line from such toll operators position automatically takes place if such desired line is found idle, whereas such telephonic extension is prevented if such desired line is found busy. More speciiically, if the desired line is found busy, the attention of the switching operator is attracted to this fact and such switching operator having determined that the call with which such desired line is already engaged is of the character over which such special service call takes precedence, she may by a manual operation cause the completion of the telephonic connection from the toll operators position to the desired line, or, if the previously established call is one over which the special service call being extended does not take precedence such switching operator may, by a manual operation, cause the breaking-down of the special service call as extended over the automatically operating machine switches and the transmission to the toll operators position of'a signal indicating the busy condition of the desired line and the breaking-down of the call as extended.

Still another feature of the invention involves the provision of signaling means associated with a switching operators position whereby the toll operator is at all times informed of the condition of the call as it is being extended or is established, the embodiment of the invention herein disclosing a progress tone which will be received by such toll operator when listening in upon her connecting circuit over which the special scrvice'call in question is extended, so long as the selection of the desired line and the testing thereof is in progress and a busy tone which is extended to such connecting circuit upon the toll operaors position. if the desired line is found unconnectible to by this special service call. The toll operator when listening in upon this connecting circuit and hearing no tone thereon. knowing that the desired line is conncctible to, and is idle if no conversation is heard thereon, or, if conversation is heard, is engaged in a prior call of the character over which the special service call being extended takes precedence. The operator may therefore in the latter event converse with the desired subscriber at her convenience, it being understood that, as herein disclosed, the extension of a special service call of a desired line busy with an ordinary or local connection, does not in terfere with the electrical or telephonic condition of the desired line except upon the manual act of the toll operator, and having conversed with such desired subscriber from time to time as may. be necessary or convenient, may either await the completion of the previous call or break down such call in the manner referred to and to be hereafter described.

Further features of the invention will sufliciently appear from the detailed description thereof in which Figure l discloses diagrammatically a toll operators position; Fig. 2 a switching operators position, together with a first group selector associated with the connecting circuit which appears upon the special switching operators po sition; Fig. 3 discloses diagrammatically the second group selector and its associated apparatus; Fig. ei discloses diagrammatically a third group selector and its associated apparatus; Fig. 5 discloses a final selector and its associated apparatus; Fig. 6 discloses the exchange ends of a plurality of subscribers lines and the apparatus associated therewith; and Fig. 7 shows diagram-inatically an established local connection.

The system disclosed as embodying the present invention will be best understood from a description of the operation thereof.

It will be assumed that the toll operator whose apparatus is diagrammatically indicated to the left of Fig. l and whose tolephonic equipment is shown at' 121 has received a call which requires to be extended to a subscribcrs station connected to the exchange network served by the automatic apparatus disclosed. The toll operator depresses her order wire key 1:22 and is there upon connected with the telephonic equipment 123 of the switching operator of the machine switching exchange and communicates to her the particulars of the desired extension. The switching operator, having received these particulars, assigns a trunk line, as, for example, that shown at 12%, in the usual manner, and depresses the assignment key 125 individual to such trunk line.

The depression of this key causes the sequence switch 100, also individual to such trunk line, to move out of its first and into its secondjposition. Such movement is caused by the energization of the relay over a. circuit including the contacts 127 of the assignment key and the sequence switch contact 102 top, the consequent energization contact 103 bottom.

In the second position of sequence switch 100, the busy lamp 193 is intermittently lighted over a circuit includin the interrupter 128 and the sequence switch contact 104: top. At this time, provided the toll operator has inserted the plug 129 into the jack 130 of the correct trunk 12 1, the relay 131 is energized due to the energization of the relay 132. This being the case, the guard lamp 133 will be prevented from lighting as the circuit for such lamp over the sequence switch contact 105 top is open at the back contact of relay 131. On the other hand, if the toll operator had inserted the plug 129 into the jack 130 of some other trunk than that assigned by the switching operator, the lamp 133 of both the trunk assigned and the trunk taken in error by the toll operator would be lighted, the one over the back contact and armature of the relay 131 and the sequence switch contact 105 top, and the other over. the front contact and armature of the corresponding relay 131 and the sequence switch contact 106 bottom or the other trunk, the sequence switch 100 of which is, of course, still in its normal po sition. c

In the second position of the sequence switch 100, the sequence switch contacts 10? bottom and 108 top are closed and a progress tone is applied to the assigned trunk so that the toll operator may be assured that she has plugged into the correct trunk and that the extension of the call is in progress. This progress tone is applied through the induction coil 139 and the interrupter 135, the sequence switch contact 109botton1 being closed at this time. Also in the second position of the sequence switch 100 a circuit is closed over the equipment searching sequence switch 190 by the closure of the sequence switch contact 110 bottom, which circuit also includes the back contact and armature of the relay 136 and the sequence switch contact 192 top associated with the equipment searching sequence switch 190. This sequence switch 190 searches for and seizes an idle registering and con trolling equipment of a switching operator in the well known manner, the test relays 136 and 137 cooperating in such selection in the usual manner, the sequence switch contact 111 bottom being closed at this time. For a detailed description of the operation of the sequence switch 190 in the association of a controlling equipment with the group selector, reference is made to applicants Patent No. 1,365,269,issued January 11, 1921.

An idle equipment having been found and seized and the relays 136 and 137 energized, the sequence switch 100 is moved out of its second position and into its fourth position over a circuit including sequence switch contact 192, top, the armature and front contact of the relay 136 and the sequence switch contact 103 bottom. The relays 136 and 137 being deenergized as the sequence switch passes out of its 3rd position due to the opening of sequence switchv contact 111 bottom and the local contact 101 of the sequence switch being open in the fourth position thereof, the sequence switch 100 stops in its fourth position. The switching operator now depresses her number keys in accordance with the numerical designation of the desired line, and such designation is taken up by the registers of the equipment taken for use. As soon as this has occurred a circuit is established in the usual manner by such equipment, including the sequence switch contact 112 top, to energize the relay 126 which closes a circuit including sequence switch contact 103 bottom, to drive the sequence switch 100 into its fifth position. In this position the operation of the tripping spindle 138 takes place in the usual manner, the circuit for the power magnet of such spindle including tle sequence switch contact 113 bottom andthe front contact and armature of the relay 126. In the operation of the tripping spindle, the usual interrupter 139, while not afiecting the re ay 126, intermittently shunts that portion of the funda mental circuit extending to the controlling equipment to cause the operation of such equipment in the well known manner. lVhen the tripping spindle 138 has taken the required number of steps to cause the brush selection required, the fundamental circuit will be opened at the controlling equipment in the well understood manner and cause the deenergization of the relay 126 which opens the circuit for the power magnet of the tripping spindle and drives the sequence switch 100 into its sixth position over a circuit including the armature and back contact of relay 126, armature and back contact of the relay 110 and the sequence switch contact 103 top. In this position of the sequence switch 100, the usual operation of the brush carriage takes place at the group selector, in dicated on Fig. 2, the circuit of the power magnet 14-1 for such brush carriage being closed over the sequence switch contact 110 top and the back contact and armature of the test relay 136. In such movement of the brush carriage, the test relays 136 and 137 operate in the usual manner to select and seize an idle trunk line of the selector group and cause the stoppage of the brush carriage by the deenergization of the power magnet 111 and the energization of the holding magnet 142 in the wellknown manner. The energization of the relay 136 in this operation causes the sequence switch 100 to move into its eighth position, the circuit for such movement including the sequence switch contact 103 bottom.

In the 8th position of the sequence switch 100, the fundamental circuit extending from the controlling equipment is extended to the second group selector shown in Fig. 3 over the sequence switch contact 114- bottom and brush 143 and the sequence switch con tact 115 top and the brush l i l respectively.

The operation of the second group selector is entirely normal and in the well understood manner, the sequence Switch 200 associated therewith being driven from its normal position by the energization of the relay 221 as soon as the fundamental circuit is closed to this switch. In the second position the operation of the tripping spindle 222 takes place. In the third position the brush carriage is moved and the relays 223 and 22st test and seize an idle trunk in the selected group and bring the brush carriage to a stop with the selected set of brushes in contact with the terminals of such idle line. In the 0th position, the fundamental circuit and later the talking circuit is extended to the third group selector by the closure of the sequence switch contacts 202 and 203 top. The movement of the sequence switch out of its first position opens the sequence switch contact 2( f and in the second position of the sequence switch 200 and subsequently the res lay 225 is energized and the relay 136 at the first group selector deenergized due to the high resistance of such relay 225. Further more in the 6thposition of the sequence switch 200 the sequence switch contact 205 top is closed, the circuit through the left winding of the relay 223 having been opened as the sequence switch left its 3rd position The operation of the third group selector shown in Fig. 4 now takes place, the relay 271 associated therewith being energized upon the closure of the fundamental circuit preparatory to controlling the third selection from the controlling equipment. The sequence switch 250 thereupon moves into its 2nd position and the tripping spindle 272 of such third group selector operates in the usual manner. Upon the completion of the operation of such tripping spindle the sequence switch 250 moves into its third position in which the movement of the brush carriage takes place in the usual manner. Upon the completion of such movement and the selection of an idle trunk line in the group selected by the operation of the tripping spindle, the relays 273 and 27 4e operate in the well known manner to seize such idle trunk line and drive the sequence switch into its sixth po sition, in which position the sequence switch contacts 252 top and 253 bottom being closed, the fundamental circuit is extended to the final selector indicated on Fig. 5.

Assume that the desired line is an ordinary subscribers line and that it is idle. The fundamental circuit being again closed at the controlling equipment, the relay 372 is energized and sequence switch 300 thereupon moves into its 2nd position in which position the operation of the tripping spindle 37 3 takes place, the circuit therefor including the sequence switch contact 303 bottom and the front contact and armature of the relay 372. The interrupter 37 4 of such tripping spindle places the usual intermittent shunt upon the portion of the fundamental circuit extending to controlling equipment over the sequence switch contact 305 bottom. Upon the completion of the operation of the tripping spindle 373 to cause it to release the desired set of brushes in the subsequent o eration of the brush carriage, the relay 3 2 is deenergized and the sequence switch 300 moved out of its second position and into its fifth position.

Before the sequence switch 300 comes into its fifth position, the fundamental circuit will be again closed in the usual manner at the controlling equipment and the relay 372 being energized over such fundamental circuit, the movement of the brush carriage will take place in the fifth position of the sequence switch 300 due to the energization of the brush carriage power magnet 377, the interrupter 37 8 intermittently shunting the fundamental circuit, with'the exception of the relay 372, in the well understood manner. The selected brushes of the final selector having in this manner been brought to the terminals of the line desired, that is, the line the numerical designation of which has been recorded by the operator upon the registering and controlling equipment taken for use, the fundamental circuit will be again opened and the relay 372 deenergized to stop the movement of the brush carriage and to drive the sequence switch 300 into its sixth position.

It should be noted that as the sequence switch 300 left its fifth position and opened the sequence switch contact 308 top, the relay 27 3 at the third group selector, which was energized over a circuit including the sequence switch contact 254 top and such sequence switch contact 308 top, is de energized due to the insufficiency of current supplied thereto through the high resistance relay 371. It will be recalled that the sequence switch 300 only left its fifth position upon the completion of the final selection to be controlled over the fundamental circuit from the controlling equipment. The de'energization of the relay 27 3 drives the sequence switch 250 out of its sixth position over the sequence switch contact 251 top and such sequence switch comes to rest in its 7th position.

The sequence switch 300 having left its fifth position now comes to rest in its sixth position, which position is utilized for the hunting of an-idle trunk line to a private branch exchange when this is necessary or desirable. In this position the sequence switch contact 304 bottom being closed a circuit is established for the relay 396 designed to be utilized for connecting toprivate branch exchange lines, each direct or ordinary line and each last line of respectlve groups of prlvate branch exchange lines, in

addition to having the usual service meter and cut-ofi' relay attached to the third or test terminal of such line, has in parallel thereto the resistance 397 connected to such terminal. The private branch exchange lines of a group other than the last such line of the group are not provided with this shunt circuit. The resistance 397 is so proportioned to the battery and the service meter 398 and the cut-off relay 399 that lines provided with the shunt circuits including such resistance, when connected to by the final V selector, will have suflicient potential upon the test terminals thereof that in the sixth position of the sequence switch 300 the relay 396 will be energized in any event, that is, whether the desired lineis engaged or idlel Consequently, in the case assumed, as the sequence switch300 comes into its sixth position, the relay 396 is energized closing a circuit over its front contact for the relay 380, such circuit including the sequence switch contact 323 and causing the energization of such relay, which in turn closes a circuit including the sequence switch contacts 324: and 311 top to drive the sequence switch 300 out of its sixth position.

The sequence switch 300, under the con trol of its local contact 301 now passes without stopping through its seventh and eighth positions. In the seventh position, the sequence switch contact 307 bottom being closed, a circuit is established from ground over such sequence switch contact, brush 276 of the third group selector, right armature and back contact of the ringing control relay 277, sequence switchcontact 257 and relay 271 to energize said relay. As a consequence the sequence switch 250 is moved out of its seventh position, to come to rest in its tenth position, over a circuit including'the sequence switch contact 258 bottom. As the sequence switch 250 is running through its eighth position, the sequence switch 300 is also passing through its seventh or eighth position. Consequently a circuit is established for the relay 372 including the left winding of such relay, se-

quence switch contact 306, brush 275 of the third group selector, the left armature and back contact of the relay 277, sequence switch contact 253 top' and sequence switch contact 256 bottom. The energization of the relay 372 closes a circuit for the right winding of the relay 385 including the sequence switch contact 308 bottom. The relay 385 energizes and closes for itself a locking circuit over its left winding, including its left armature and front contact and the front contact and armature of the relay 371. V

It is the energization of the relay 385 at this time which causes the differentiation of the operation of the final selector shown between that when used for the purpose of extending a call over the toll operators position and that when used to extend anordinary or local call from the machine switching exchange of which it forms a part. It will be observed that the control of this relay is exercised from the third group selector, this'third group selector being one of the relatively few such third group selectors over which trunk or toll calls may be extended in the manner described. The final selector shown, if it had been connected to by ordinary third group selectors, that is, a group selector carrying the usual or ordinary local service,- would have operated substantially in the manner of ordinary final selectors, as will be hereinafter described, since such ordinary third group selectors would not be provided with the necessary means to cause the energization of the relay 385 as has just be described.

Continuing the description of the extension of a call from the toll operators position to a line assumed to be an ordinary. line and idle, the eighth position of the sequence switch 300 through which it passes without stopping is a testing position andin this position the line will be tested by the relays 379 and 380 in the usual'manner and as suchline is assumed to be idle is seized and has a busy guard placed upon the test terminal thereof by the operation of the relay 379. QThe operation of the relay 380 closes a circuit to drive the sequence switch 300 through its ninth position and into its tenth position where the sequence switch contact 324.- being open and the relay 385 energized,it stops. In this position the sequence switch contact 307 bottom is open causing the movement ofthe sequence switch 250 .into talking position as will be hereinafter described, and the sequenceswitch contact 307 top and 322 bottom are closed to connect the call; as extended to the subscribers line through'the condensers 331 and 332. Furthermore, as the relay 385 is at this time energized and the sequence switch contact 323 is open, circuitv of the test relays 379 and 380 is open and no ground exists thereon. Consequently the called line is not made busy and is free to call and be called in the usual'manner, the extension thereto through the condensers 331 and 332 afiecting it in no way and serving only for purposes to be hereinafter described. a

The opening of the sequence switch contact 307 bottom as described, when the sequence switch 300 comes into its tenth position, causes the denergization of the relay 271, which thereby closes a circuit over the sequence switch contact 259 to drive the sequence switch 250 into its thirteenth position which is the talking position of this sequenceswitch.

During the operation of the registering and controlling equipment to control the second and third group selectors and the final selector, the relay 126 was maintained energized, as is usual in systems of this character, over a circuit extending from such equipment to such relay, includin the sequence switch contact 112 bottom. s is also usual in systems of this character, imme diately upon the completion of the final selection controlling operation of this, equipment, the circuit for such relay 126 was opened at the equipment, and such relay dc energizing drives the sequence switch 100 out of its eighth position and into its ninth position. 7

In the ninth position, assuming that the toll operator has inserted the plug 129 into the jack 130, a circuit is found to drive the sequence switch into its eleventh position, such circuit including the front contact of the relay 131. and the sequence switch contact 106 top. In. the eleventh position of the se.- quence switch 100, the relay 14.10 is deenergized, although such relay has been butinomentarily energized due to the briefclosure of a circuit including the sequence switch contact 260 of the third group selector, and

thenreleased, the desired line being idle,'the sequence switch 250 having been moved out of its tenth position and the sequence switch contact 260 opened. .Therelay 140 being, therefore, denergized, the sequence sw1tch 100 will be moved direct into its-thirteenth position, which is the talking position of this sequence switch. In this position the progress toneis removed from the trunk-line extending .to the toll operators position,

' the sequence switch contacts 107 bottom and 108, top being opened. The connection is now'established directly from the cord circuit appearing on the toll operators position through to. the desired subscribers line,

such circuit including, onthe one hand, se-- quence switch contacts 107-top and 108 bottom, and, on the other 'hand, condensers 331' and 332. When the sequence switch 100 Ieftitseighth position, the circu t connect ing busy lamp 193 through nterrupter for such lamp direct to ground was connected over the sequence switch contact 116, so that this lamp which had, up to that time, been intermittently lighted, is now continuously lighted to indicate to the operator that theselection controlling operations have been completed. The guard lamp 133 is now extinguished.

The toll operator ma now listen in upon the desired line and, hearing no conversation taking place thereon, may proceed to complete the connection or may wait until such time as the completion of the. connection may be desired. if she does not imincdiately complete the connection, she may at any time listen in upon the desired line and, if the desired line is then busy. may inform the subscriber thereon of the fact that a toll call is awaitinghis attention, and may breal: down. the then existing local connection as will be hereinafter described. On the other hand. assuming that the subscribers line is :till free, all that is necessary for her to do is to operate the ringing key M5 to apply ringing current to the connection as extended from her position. As a. matter of fact, the ringing current as actually impressed upon the connection by the action of the ringing key 1 15, does not reach the subscribers station to operate the signal located thereon, but there is no reason w y it is nee essarythat the toll operator should be aware of this fact. it being necessary for her to know only that, having been connected tothe desired line, such line being idle, it is merely necessary for her to operate her rin ing key in order to complete the conncc and cause the signaling of the desired sub scri-aa. 'To acunnplish this, the operation of theringing key 14-5 serves tOQIlGlQlZQllli-E relay 8 at a thire group selector. the circuit including the condenser 279. the relay either 278 being adapted to he energized l1} alternating or direct current. Each time the relay 278 is euergizml by the operation of e ringing key 1&5, it closes a circuit for clinging control relay 277. which relay is therefore correspondingly energized and connects over its front contacts ringing current to the brush 276 and grounr. to the brush 275.

The connection of ground to the brush 2'75 causes the energization of the relay 372 over the sequence switch contact 306, and

and fri'int contactof the relav385, the right winding" of the relay 372. the left winding of the relay sequence switch correct 309 bottom and relay 384. The sequence switch 300 will stopin its sixteenth position, however, due to the opening of the sequence switch contact 302. The desired subscribers line'is now being rung directly from the armatures of the relay 277, the sequence switch contacts 313 top and 316top closing a direct metallic path between such armatures and the desired subscribers substation. Preferably, but not necessarily, the condensers 331 and 332 are so proportioned that, although the toll operator may listen in upon the desired line and may converse with the subscriber thereon, they will not allow the transmission of sufficient ringing current to such line and the ringing of the subscribers line will only take place when the sequence switch contacts 313 top and 316 top have been closed as described.

Upon the response of the called subscriber no'fur her operation of the group selectors or final selector or the apparatus associated therewith is necessary, the called subscribers line being connected directly to the repeating coil 280 and supplied with battery therefrom over the sequence switch contacts 256 top and 261, such repeating coilon the other hand being connecteddirectly to the connecting circuit 1416 upon the toll operators position, the sequence switch 250 being inits thirteenth position,-the sequence switch 200 being'in its sixth position and the sequence switch 100 being in its thirteenth position.

Upon the termination of conversation after a successful call as described restoration takes place under the controlof the toll operator as is customary. The initiation of therestor'ationof the selector switches takes place upon the removal by the toll operator of the'plug 129 from the jack 130. This causes the deenergization of the relay 132 and the consequent deenergization of the relay 131, and the sequence switch 100 is driven out of its thirteenth and into its seventeenth position by a circuit including se-' quence switch 105 bottom and the back contact and'armature of the relay 131. In the seventeenth position of the sequence switch 100, the first group selector brush carriage is restored to normal position in the usual manner and such restoring movement being completed the sequence switch 100 is moved into its eighteenth position. In this position a circuit is again established over the armature and back contact of the relay 131 and the sequence switch contact 105 bottom and the sequence switch returns to its first or normal position.

It may be noted that, the sequence switch contact 113 top being closed from the fourteenth to fourth position, the tripping spindle 138 will be restored by the operation of the lower contactsof the interrupter 139 inample time for a subse uent connection even in the case of a premature release, since in the new connection to he established such tripping spindle is not required until the sequence switch 100 reaches its fifth position.

Immediately that the sequence switch 100, associated with the first group selector, left its thirteenth position in the restoring operation just described, the circuit of the relay 225 was opened at the sequence switch contact 111 top and the second group selector, both the brush carriage and the tripping spindle thereof, and the sequence switch 200 associated therewith are restor d to normal in the well understood manner.

Correspondingly the movement of the se quence switch 200 out of its thirteenth position opens the circuit of the relay 281 at the sequence switch contact 205 top and the third group selector with the brush carriage and tripping spindle thereof and the sequence switch 250 associated therewith are restored to their normal positions in the usual manner.

As the sequence switch 250 left its thirteenth position. th circuit of the relay 371 is opened at the sequence switch contact 254; top, the deenergization of such relay driving the sequence switch 300 into its seventeenth position wherein, if the called subscriber has not as yetrestored his receiver to its switch hook, the relay 312, is energized over a circuit including the sequence switch contact 312 bottom, the'subscribers line, the sequence switch contact 313 top and the sequen e switch contact 30'? bottom. The relay 372 being deenergized, however, by the fact that the receiver of the called subscriber has been restored to its switch hook,

. the sequence switch 300 driven out of its seventeenth position and into its eighteenth position by a cir uit including the armature and back contact of relay 372 and sequence switch contact 30 1 top.

In the eighteenth position of the sequence switch 300 the brush carriage of the final e ector is restored the well understood manner, and, iaving been restored, the sequence switch 300 is driven into its first or normal position. The tripping spindle 373 has already been restored, the sequence switcn contact 303 having been closed in the twelfth position of the sequence switch. 300. In order that successful call which has been established to the alled subscribers lin jfrom the toll operators position may not be distin-hed when established, only such calls will traverse third group se lectors provided with means, snch'as the sequence switch contact 256 bottom to apply at the proper time. a ground connection to the brush 275 of the third group selector, and all such calls will pass over a third group se ector of this character.

I l n Consequently n the GXiQRSlOl']. o'l' all toll ca ls &

to a final selector of the character disclosed, the relay 335 will be energized and locked up in the seventh or eighth position of the sequence switch 300, whereas in the extension of ordinary calls over such final selectors, such relay will only be energized in the seventeenth position of such sequence switch.

The relay having been energized, the call assumed being a toll call, when the sequence switch 300 came into its thirteenth position the relays 383 and 38d were energized over a circuit including the armature and front contact of the relay 371, left armature and front contact of the relay 385, the right winding of the relay 37 2, the left winding of the relay 383, sequence switch contact 309 bottom, and relay 384. The attraction of the left armature of the relay 38 i closes the circuit through the winding 329 of the busy tone induction coil, the interrupter 328 and the tone producing apparatus 351. The attraction of the right armature of the relay and the armature of the relay 383 closes in the sixteenth position of the sequence switch300, that is, the talking position thereof, a circuit connected to the test terminal of the desired line and therethrough to the test terminal of such line on all of the other final selectors having access thereto,

including the brush 333, front contact and right armature of the relay 38 1 and front contact and. armature of the relay 383, and

. the winding 33'? of the busy tone induction Emtcnsiov'z of a local caZZ to (midle desired Zinc.

'Fig. 7 shows diagrannnatically an established connection between a local calling line lOO and a called line. The final selector indicated at 4:01 is the same as the switch shown in detail in Fig. 5 and is in fact available for toll connections aswell as for local connections. 1

In the case where the idleselector such as shown in Fig. 5 is used for a local call, the relay 385 will not be energized in the seventh or eighth position of'the sequence switch 300. Assuming that the desiredli-nc'was idle,:the relay 380 is energized in the eighth position of the sequence switch 300 and is maintained continuously energized therea ter until the breaking down of the call after the completion of conversation by a circuit including back contact and left armature of the relay 385 and the front contact quently thesequence switchv 300 will not stop in its ninth, tenth or eleventh positions but will continue in motion until it reaches its thirteenth position. In this position ringing automatically takes place under the control of the interrupters 326, 381 and which are coupled together and, as indicated, rotate in a counter-clockwise direction. Tminediate ringing takes place by the closure of the sequence switch contact 312 top and the sequence switch contact 313 bottom. The sequence switch remains in its thirteenth position until, due to the rotation of the interrupter 381, a circuit is closedincluding said interrupter and the sequence switch contact 314: to energize the relay 372 to drive the sequence switch 300 into its fourteenth position. The ringing will be continued in the fourteenth position of the sequence switch and said sequence switch will remain in such position until, due to the subsequent closure of a circuit including the interrupter 382 and the sequence switch contact 315, the re lay 372 is again momentarily energized to drive the sequence switch: 300 into its fifteenth. position. In this position the sequence switch contact 312 top being opened, the continuous ringing of the desired line ceases, and there is substituted therefor, over the sequence switch contact 316 bottom, intermittent ringing controlled by the interrupter 326. V 7

At any time during the ringing, that is, while the sequence switch 300 is-in its thir-' teenth, fourteenth or fifteenth position, that the called subscriber responds by removing his receiver from its switch hook, the relay 3831's energized and the sequence switch 300 is immediately driv n talking position thereby establishing the through connectionto the desired subscriber and cutting off the ringing of such' subscriber. V

The restoration of the final selector after the establishment of a connection on a call of this character takes place in the usual manner, being initiated byrthe de'energization of the relay 371 and being delayed in the seventeenth position of the sequence switch 300 until the called subscriber has restored his receiver to its switch hook. In

a connection of this character, it willbe obnary or local call to a desired subscriber over a final selector switch of the character shown in Fig. 5, such desired line has been found busy, either with a local call or with In this case relays 3. 9 and 380 a toll call. would not be energized in the eighth position of thesequence switch 300, and the s'e quence switch 300 would stop in. its ninth positionv In tlus'position abusy tone would into its sixteenth or into its seventeenth such position (the re ay 372 belng deener- "gized) and the eighteenth position (the be heard by the calling party, if the local network is of the full automatic type, or by the semi-automatic operator or such operator and the calling party as may be prequence switch contact 309 top causes the in-' termittent energization, due to the interrupter 327, of'the relay 384 which in turn causes the intermittent connection of the interrupter 328 and tone producing device 351 to the winding 329 of such busy tone induction coil. r I

The relation of the interrupter-327 to the interrupter 328 is such that these interrupters being coupled together the circuit willbe closed through the interrupter 328 at all times when the circuit is closed through the interrupter 327, the circuit through the interrupter 328 being closed for a longer period, however, than the circuit through the interrupter 327, for purposes which will be hereinafter described. The calling subscriber or the semi-automatic operator hearvingthe busy tone w1ll cause the breaking down of the connection, as it has been entended, in the usual manner. The deenergization of the relay 371 so produced drlves the sequence switch 300 into its eleventh position in which position the restoration of the switch carriage takes place in the well known manner, upon the completion of which sequenceswitch 300 is driven into its twelfth position where the circuit over the armature and back contact of the'relay 371 ,40

and sequence switch contact 318 being again estabh shed, the sequence switch 300 is driven ositlon and through brush carriage being in its normal position) into its normal positlon.

Extension of toll call to local busy subscribers Zine.

scribers line,-the sequence switch 300 passed through its eighth position such line-was found to be busy in ,connection'with a local or ordinary call. The relays 379 and 380 are therefore not energized and the sequence switch 300 stops in its ninth position. In this position thefswitching operator hears a busy tone precisely as the calling subscriber or the semi-automatic operator in the extension under similar circumstances of an'ordi- .nary call. This busy toneis, however, an

of the relay 384 had retracted, as it has been "assumed that the call with which the desired line was busy was a local or ordinary one.

its the sequence switch 300 left its fifth position, the sequence switch 250 was moved into its seventh position and as the sequence switch 300 came into its seventh position, the sequence switch 250 was moved out of its seventh position in the manner hereinbefore described in connection with the extension of a toll call to an idle line, In the tenth position of the sequence switch 250, therefore, since the sequence switch 300 has stopped in its ninth position, a circuit is established'and maintained for the relay 271 over the sequence switch contact 257, the brush 276, and the sequence switch contact 307 bottom. Furthermore a circuit closed in the seventh position of this sequence switch is maintained in this position through the sequence switch contact 260 (around the condenser 279 and the condenser 262 in the second group selector side of the repeating coil 280), for the relay 278 in series with the supervisory relay 140 at the first group selector. This circuit was closed before the sequence switch 100 at the first group selector reached its eleventh position and such sequence switch therefore stops in its eleventh position. Both the relay 271 and the relay 278 being energized at this time the sequence switch 250 stops in its tenthposition. It may be noted that the sequence switch 100 was driven outof its eighth position and the sequence switch 300 out of its fifth position practically simultaneously. As thesequence switch 250 was driven out of its sixth position, immediately upon the movement of the sequence switch 300 from its fifth position, the sequence switch 250 will close the contact 260 to energize the relay 140 as described, before the sequence switch ()0 can possibly have come into its eleventh position.

In the eleventh position of the sequence switch 100 in which it now rests, the circuit of the busy lamp 133 is closed through the interrupter 128 by a closure of the sequence switch contact 104 bottom; The flashing of the busy lamp indicates to the operator that the desired line is busy. She thereupon, in order to determine whether it is locally busy or busy with a direct toll call, depresses her listening key 147 and listens in on the line as-extended and is able .to determine from the tone impressed thereon that the desired line is locally busy. This connection of her telephone set 123 takes place over the center contacts of the listening key 147 and the sequence switch contacts 114 top and 115 bottom. The impedance of the relay 140 and the impedance coil 148 is sufiicient to allow her to efiectively listen in upon the call as extended. The closure of the bottom contact of the listening key 147, when operated by the switching operator, causes the cutting olhfor the time being, of the order wire from the switching operators telephone set. Having determined that the desired line is only locally busy, the switching operator, while her listening key 147 individual to the connecting circuit which is in use is still depressed, operates the common advance key 149 of her position, which closes a circuit to drive the sequence switch 100 out of its eleventh position and into its thirteenth position, which, as has been noted, is the talking position of the sequence switch.

As the sequence switch 100 leaves its eleventh position, the sequence switch contacts 11 1 top and 115 bottom are opened and as the sequence switch contacts 107 top and 108 bottom are not closed until the thirteenth position o fthis sequence switch, the circuit which has energized the relay 278. at the third group selector in series with the relay 140 at the first group selector is opened and such relay 278 deenergizes, closing a clrcuit including the sequence switch contact 202 top to drive the sequence switch 250 into lts thirteenth position. 111 passing through its eleventh position, a circuit is established including the armature and front contact of the relay 271, the sequence switch contact 258 top, the sequence switch contact 253 top, back contact and left armature of the relay 277, brush 275 and sequence switch contact 306, to energize the relay 372, wherebythe sequence switch300 is moved out of its ninth position and into its tenth position, in which position, as has been before described, the call is further extended to the desired'line through the condensers 331 and 332, although the relays 379 and 380 being deenergized no busy guard is placed upon such desired line by the final selector in question.

Thet'oll operator may now listen in by the depression of her listening key 150 and will no longer receive theprogress tone produced by the tone repeating coil 139 as the sequence switch contacts 107 bottom and 108 top are now opened. Having listened in she may converse with the wanted subscriber and in- .form him that as his line is desired in connection with a toll connection, she is going to break down the already established local connection for the purposes 01" such toll conneetion. To accomplish this, the operator depresses the ringing key 145 precisely as though. she were ringing a desired idle line, as has been hereinbefore described. Therelay 278 is, as a consequence, energized and, the sequence switch contact 263 being closed, produces the energization of the relay 27 7. A. ground is thereby placed upon the brush 275 and the relay 372 is energized to drive the sequence switch 300 out of its 10th position and into its thirteenth aosition, through which position, as well as its fourteenth position and fifteenth position, it will be moved, due to the energization of the relays 372, 383 and 38-1, by the closure of the sequence switch contact 309 bottom, th relay 335 having been energized and locked up in the seventh or eighth position of the sequence switch 300, the call being extended being a toll call. Due to the opening or" the sequence switch contact 302,- the sequence switch 300 comes to rest inits sixteenth position.-

As the sequence switch 300 was passing through its thirteenth to fifteenth positions, a circuit was closed by the sequence switch contact 317, the relays 383 and 38% being energized, to connect a direct path from ground to the test brush 333, which is now in contact with the test terminal of the desired line. This direct path to ground causes the shunting and falling oil" of the test relays of the switch (final selector or first line finder) by which the desired line is connected to the connection with which it has been previously engaged and the consequent breaking down of such previous connection. It should be noted, however, that although by this means the previous local connection is effectively broken .down the condition by which such breakdown is accomplished is removed when the sequence switch 300 comes into its sixteenth or talking position and the normal busy guard produced by the operation of the relays 379 and 380 is restored, so that no detrimental effect can take place in other final selectors testing for the desired line which has now been seized. In the sixteenth position, there is also, as has been previously described, placed upon the test terminal of the desired line a busy guard indicative of the fact that the desired line is engaged in a toll call, the

ratus will take place as hereinbefore described in connection with a successful call to an idle desired line.

Attempted connect/ion to a toll busy desired line.

The attempted connection with a toll busy desired line takes place precisely as has been described with regard to the con-- nection with a local busy desired line up to the point where the sequence switch 300 comes into its ninth position. The sequence switch 300 is now in its ninth position, the

sequence switch 250 is inits tenth position bus although such "interrupters being position, as has been hereinbefore described.

Responsive to the flashing of the busy lamp 133, the switching operator depresses her listening key and hears a combination of toneswhich'indicate to her that the desired line is'busy in a previously established toll connection. This combination of busy tones is produced in thefollowing mannerzlt will be 'recalled that'when a final selector has seized a desiredline fora toll call the sequence. switch 300, associated with such final selector in its sixteenth position "has' closed a circuit including the winding 1 15 337 of the busy tone repeating coil, the armature and front contact of the relay 383, the right armature and front contact of the relay 384, and the brush 333 of such final selector. Since, at the same time, a circuit is closed for the winding 329 of the busy tone repeating coil through the leftarmature and front contact of the relay 38 4 and the interrupter 328 to the tone producing apparatus indicated, an intermittent tone measured by the period the interrupter 328 closes the circuit'last described is applied to the test terminal of'the line seized. Ashas been before mentioned, the period of closure of the interrupter 328 is greater than the period of closure of the interrupter 327 coupled and preferably common 'tothe-exc ange, the

interrupter 328 is closed at all timesthat the interrupter 327 is closed.

The switching operator in 'the subsequent apparatus through the interrupter 328 and the front contact and left armature of the relay 384, while such relay 384 is intermittently" energizedby the interrupter 327 as has been described. As such interrupter 327 opens, however, the armatur'es of the relay 384 retract and, while the left armature of such relay moves from its front to a back contact, no further tone is received by the "switching operator. Immediately, however,

that suchleft armatur'e'reaches its back contact, the busy tone" will beheard by her which" is impressed upon the test terminal ';of the desired line due'tov the prior estab- "lishment'to such desired'line of another toll and therefore restores her listening key 147 to normal positionandoperatesthe assignment'key 125 associated-with the connecting circuit shown together with the common release key 150 of her position. This causes the energization of the relay 151, which closes a locking circuit for itself over its left inafter described, the sequence switch contact .117 is closed to shunt the winding of such relay and causes its deenergization. The

resistance 152 is provided for the usual purpose of preventing damage to the battery when this shunt circuit is closed. 7

Upon the 'energization of the relay 151 and the restoration of the assignment key 125,

a circuit is" established including the central normal contact of the assignment key 125, the sequence switch contact 118 top and the right armature and contact of the relay 151, to drive thesequence switch 100 out of-its' eleventh position and into its seventeenth position. In the fifteenth to'eighteenth positions of the sequence switch 100 the toll busy tone is impressed upon the trunk line 124 extending to the toll operators position, the sequence switch contact 107 bottom, 108

top and 109 top being closed. This toll busy tone is shown as differentiating from the progress tone by the interposition of the interrupter 153 in the circuit of the interrupter 135, but such toll busy tone may be obviously produced in any desired manner.

As the sequence switch 100 was leaving its thirteenth position in' moving from its eleventh into its seventeenth position as just described, the initiation of the restoration of the second group selector took place by the opening of the sequence switch contact 111 as hereinbefore described. Consequent upon the operation of the restoration of the second group selector so produced, the restoration of the third group selector was initiated in the manner hereinbefore described, and similarly the restoration of the final group selector, restoration in this case of the final group selector taking place from the ninth position of the sequence switch 300, the sequence switch being driven out of its ninth and through its tenth position by the deenergization of the relay'371, the brush carriage of thefinal selector being restored in the eleventh position of such sequence switch which is then moved into its thirteenth position. From this position the sequence switch will be moved into its seventeenth position by the continued'deenergization of the relay 371, in which position, the relay372 being deenergized the brush carriage having been restored, it will continue in motion-to its eighteenth position, in which position in turn the interrupter 378 being in its normal position,-the relay 372 will be energized to drive the sequence switch 300 into its first or normal position over a circuit including the sequence switch contact 302. All of the l apparatus of the second and third group Solectors and the final selector is thus restored to normal. Upon the coming of the sequence switch 100 into its seventeenth position, the restoration of the brush carriage and the first group selector takes place and the sequence switch 100. passes: into its eighteenth position. In this position the sequenceswitch 100 awaits the removal by the toll operator of the plug 129 from the jack 130 after she has heard the toll busy tone from the switching operators position produced as above described. When, due to the removal of'such plug 129, the relays 132 and 131 are denergized in the eighteenth position of the sequence switch 100, such sequence switch is restored to its first or normal position by a circuit including the armature and back contact of the relay-131 and the sequence'switch contact 105 bottom.

Pm'oatc branch exchange trunk lines.

" In-the group or groups of final selectors provided for-operating to select an idle one of a group of private branch exchange trunk lines which group or groups of final selectors may comprise the whole or only a part of the final selectors of the exchange, the private branch exchange trunk lines of a group except the last trunk line "ofthe group are differentiated from such last trunk lines of groups and private or ordinary subscribers lines by the fact that the cut-off relays 399 and. message registers 398 are not shunted by the resistance 397 as indicated in connection with the ordinary or direct subscribers line 393 shown at the upper part of the right .hand side of Fig; 6 or the last private branch exchange trunk line 395 of a group as shown at the lower part of the right hand side ofFig. 6. Such a private branch exchange trunk line other than the last trunk line of such a group is indicated at 394, the lines 394 and 395 are assumed to'form a group of private branch exchange trunk lines, the

final selectorin testing such group first'testing the line 394 and subsequently line 395 if theline 394 is found busy. It is obvious that this group, although shown as comprising only two private branch exchange trunk lines may comprise three, or more of such trunk lines all of the trunk lines of such group beingarranged similarly to such line 394 except the last line'of the group, 395,

which has connected to itstcst terminal the resistance397 ina manner hereinbefore described. i

The extension of a connection to a private branchexchange trunk line takes place precisely in the same manner as in the case of an extension of'a connection to an ordinary subscribers line, except in regard to the sixth position of the sequence switch 300.

'To, connect with a private branch exchange trunk line, the numerical designation inditrunk line of the group selected. private branch exchange trunk line is also cated by the operator upon her number keys is always the numerical designation of the terminals of the first private branchexchange trunk line. Consequently when the sequence switch 300 comes into its sixth position, the brushes of the final selector rest upon the terminals of the first private branch exchange trunk line of the group leadingto: the private branch exchange to which connection desired. If such first trunk line of the group is idle, the relay 396 will be energized, causing the energization of the relay 380, as has been before described and. the sequence-switch 300 passes out of its sixth position to again test the desired busy the brush: carriage continues in motion. As soon,"howevcr, as the brushes of the final selector come into contact with an idle private branch exchange trunk line of the group, the relay 396 is energized followed by the energization of the relay 380 opening the circuit of the power magnet 377 and closing the circuit including the" sequence switch contact 311 top to drive the sequence switch 300 out ofits sixth-position from whence the operation'of the final selector and the sequense switch 300 takes place as has been hereinbefore described.

Assuming that all of the private branch exchange trunk lines, except the last trunk line of the group, are busy, the brushes of the final selector will finally come in contact with the last private branch exchange trunk line of the group such as the line 395.:

When this occurs, whether such'last trunk line of the group is busy or idle, the relay 396 will'be energized due tothe connection of the circuit including the resistance 397 with the test'terminal of this trunk line. -The sequence switch 300 will therefore be driven out of its sixth position. In passing through its eighth position, the relays 379 and 380 will test the line 395 to determine whether it is busy or idle. If it is found idle, the extension of the call will proceed precisely as has been described in connection with the extension of a call to an idle If thisordinary or direct subscribers line; On the other hand,- if the line 395 is found busy, the

switches," means at said second position for controlling the operation of said second operation of the final selector vapparatus thereafter takes place precisely as in the case of an ordinary or direct subscribers line which is found'busy, that is, among other things the busy, tone will, be returned to the switching operator and she will be able to determine whether such line is locally busy or toll busy, and, it locally busy, the local call may be broken dOWn by the toll operator in the manner hereinbefore described.

What is claimed is: 1. In a telephone exchange system, a calling line, a called line, means for, establishing a connection between said lines, means for rendering the called line busy during such connection, a second calling line, an operators' position, a second operators position, means at said first position for extending thesecond vcalling line to said second position, a series of automatic switches, means for operating said switches to extend the second calling line to said called line, means for. notifying the operator at said sec-' ond position of the-busy condition of the 25 called line, and means under the control of saidfirst operator for releasing said first connection. I a

2. In a telephone exchange system, a call ing line, a called line, a series of switches for establishing a connection betweensaid lines, means .for renderingthe called line busy during said connection, a second calling-line,an operators position, a second operatorspositlon, means at said first position for extending the second calling; line to said: second position, a second series of series ofswitches to exte'ndthesecond call: ing line'to said called line, means for notifying the operator at said second" position of the busy condition of the called line, and means-underthe control ofithe'first operator for releasing said first connection. 3. Ina telephone exchange system, a calling line, a called line, a series of switches for establishing a connection between said lines, means for rendering the called line busy during said connection, a second calling line, an operators position, a second operators. position, means at said first position for extending the second calling line to said second position, a second series of switches,

means at said second position for controlling theoperation of said second series of switches to extend the second calling line to said called line, tone producing means for notifying the operator at said second position of the busy condition of the called line,

and means under the control of the first operator for releasing said first connection.

4. In a telephone exchange system, a calling line, a called line, a series of switches for 1 establishing a connection between said lines,

means for rendering the called line busy during said connection, a second calling line, an operators position, a second operators position, means at said first position for extending the second calling line to said second position, a second series of switches, means at said second position for controlling the operation of said second series of switches to extend the second calling line to said called line, means for notifying the operator atsaid second position of the busy condition of the called line, and a manually operable key at the first operators position for releasing said first connection. I 5. In a telephoneexchange system, a calling line, a plurality of final selectors, '2. called line having terminals in said selectors, a series of switches including one of said, selectors for establishing a connection between said lines, means for rendering the called line busy, a second calling line, an operators position, a second operators position, means at said first position for extendplurality of switches, a called-line having test terminals in said switches, means including one of said switches for establishing a connection between said lines, means for placing a condition on the test terminal to render the called line busy, a second calling line, an operators position, a second operators position, means at said first position for extending said second calling line to the second operators position, means including one of said switches for extending the second calling line to said called line, means for notityin the operator at said second position of the busy condition of the called line, means controlled by the operator at said first position for changing the condition on the test terminal of the called line, and means responsive to such change for releasing said first established connection.

7. In a telephone exchange system, called lines, calling lines of two different classes, a series of switches for establishing a connection between a calling line of one class and one of said called lines, an operators position, a second operators position, means controlled by said operators for extending a connection from a calling line of the other class to said called line, means for notifying the operator at said second position of the character of the calling line that is connected to the called line, and means under the control of said first operator for releasing said first connection.

- 8. In a telephone exchange system, called lines, calling lines of two different classes, a series of switches for establishing a connection between a calling line of one class and one of said called lines, an operators position, a second operators position, means controlled by said operators for extending a connection from a calling line of the other class to said called line, tone producing means for notifying the operator at said second position or" the character of the calling'line that is connected to the called line, and means under the control of said first operator for releasing said first connection.

9. In a telephone exchange system, called lines, calling lines of two different classes, a

series of switches for establishing a connection between a calling line of one class and one of said called lines, an operators position, a second operators position, means controlled by said operators for extending a con- :nection from the calling line of the other class to said called line, means iorproducing a plurallty of diflerent tones for notlfylng the operator at said second position of the character'of the calling line that is connected to the called line, and means under the control of'the operatorat said first position for releasing said first connection.

10. In a telephone-exchange system, called lines, calling lines of two different classes, a plurality of final selector switches, means including one of said switches for establishing a connection between a calling line of either class and one of said'called lines, an operators position, means for' producing a plurality-of tones of different character to inform the operator of the character of the calling line that is connected to a called line when asubsequent connection is extended to such called line, and manual means for re- V plurality offinal selector switches, said called lines having terminals in said switches, means including one of said switches for establishing a connection between a calling line of either class and one of said called lines, an operators position, means for producing a plurality of tones of different character to inform the operator of the character of the calling line that is connected to a called line when a subsequent connection is extended to such called line, and manual means for changing the condition of saidterminals to release said first connection as soon as a subsequent connection is extended to the called line. r V

12. In a telephone exchange system, a calling line,.a plurality of final selectors, a called line having terminals in said selectors, a

series of switches including one of said se-- lectors for establishing a connection between sald lines, means for rendering the called line busy during said connection, aQsecond calling line, an o'perators position, a second series of switches includingone of said selectors for establishing a connection between said second calling line and said icalled line,

' means for-informing the operatorof the busy condition ofthe called line,-means controlled by the operator for grounding the called line terminals, and means responsiveito the-- grounding of said terminals for releasing said first; connection, said .groundbeing re moved as soon as the release of said first PLIPA PoLINKowsKY, 

